Electrical means for producing musical notes



June 30,1925. 1,543,990

L. DE FOREST ELECTRICAL MEANS FOR PRODUCING-MUSICAL NOTES Filed April 24, 1915 Patented June 30, 1925.

UNITED STATES 1,543,990 PATENT OFFICE.

LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO DE FOREST PHONOFILM CORPORATION, OF JERSEY CITY, NEW JERSEY, A CORPORA- TION or DELAWARE.-

ELECTRICAL MEANS FOR PRODUCING MUSICAL NOTES.

Application filed April 24, 1915. Serial No. 23,700.

To all whom it may concern:

Be it known that I, LEE or: Fomasr, a citizen of the United States, residing in the city of New York, county of Bronx, and State of New York, have made a certain new and useful Invention in Electrical Means for Producing Musical Notes.

My invention relates to. electrical means for producing musical notes or other sounds.

The object of the invention is to provide means for electrically reproducing sustained musical notes of any desired pitch.

Further objects of the invention will appear more fully hereinafter.

The invention consists substantially in the combination and location of parts and the circuit arrangements employed in connection 'therewith, all as will be more fully hereinafter set forth, as shown in the accompanying drawing, and finally pointed out in the appended claims.

Referring to the drawing,-

Fig. 1 is a dia rammatic view showing one arrangement or accomplishing the objects and pur oses of my invention.-

Fig. 2 is a etail view of a modified switch arrangement as used in connection with my invention.

In accordance with m invention I emplo an exhausted glass ulb 1, such as an au ion, which, in the form shown, contains the usual hot filament electrode 4 and the cold plate electrodes 2 and the input or grid electrodes 3, preferably, but not necessarily located between the filament and plate electrodes, as shown. A source of current, such as a battery 6, heats the filament electrode and a variablecontrolling resistance 5 is included in the filament circuit to control the amount of current from the source 6. For

the purposes of illustration I have shown g vice 20. In the form shown these conde'n sers are connected in parallel, and one terminal of the parallel circuit is oonnectodto form one leg of the filament circuit through a circu1t containing "one winding 10.01? a transformer. Shunted around the coil 10 is a variable capacity such as a variable condenser 12.

The other winding .11 of the. transformer the same side thereof as is connected one terminal of the coil 10 as hereinbefore described. In shunt around the secondary coil 11 of the transformer, or in shunt around the secondary coil 11 and the coil of the receiver or reproducer 8 which are connected inseries in the form shown, is another capacity for which I. find it preferable to employ a variable condenser 13. It will be readily seen and understood that while certain adva'ntagps to be hereinafter described are obtained y thus associating a variable capacity around the secondary coil of the transformer, it is not essential for the objects and'pu'r oses of. my invention, and .I am not, there ore, to be limited or restricted in this detail.

Connected between the grid and filament electrodes of the audion is a series of high resistance paths, indicated at 22, 22, preferably non-inductive, comprising, for exam ple, ground glass, graphite marks or other 'gh resistance materials. The total resistance of this leak ath should be from 5,000 to 10,000 ohms. everal taps are taken from the leak path and each tapis adapted to complete the electric circuit between the rid and the filament electrode by means of the switches 17, 18, 19,- 20, 21, etc, one switch beingprovided for eachtap. The switches may be of any construction, butpreferably in the form of piano ke as, adapted to close their respective circuits ylight pressure of the fingers.

- -I have "fo'undthat when an audionds -lc'onnected as above des c"ribed,'; periodic current charges are set up in thegrid-filament' circuitand also in the associated plate-filament circuit, capable of producingdn a tele hone receiver or othersuitablesoundrepro ucer, sustained musical notes of'a remarkable clearness and purity of tone. The pitch or periodicity of these sounds, depends, among other things, upon the inductance in the as soc ated circuits, the capacities of the various condensers and also in the amount of resistance in the high resistance ieal: path. I am enabled, therefore, by varying these elements at will, to produce any desired note or tone in the receiver or reproducer 8. Inc general pitch of be instrument is once determined by B, by the bloclz' 16. con cted in s closing cither ijey alone.

Many other v-sars will at once themselves to those filed in the art for} during notes of desired pitch. By associating two or more such oscillating audions and circuits. an endless variety of notes, chords and tonal ariations may be obtained, therei'orc. while I have shown and described but one instrument, it will be understood that any number of instruments may be associated with each other, in the broad scope of my invention, and thus produce many novel and distinctively beautiful musical effects.

By gradually varying a condenser, for example, 12 or 13, the change of pitch is made continuous, and thus, a siren note having a wide range of pitch is obtained.

Having now described the objects and nature of my invention, and one arrangement for the accomplishment thereof, what I claim as new and useful and desire to secure by Letters Patent, is,

1. An electrical tone producer including an audion having plate, gridand filament electrodes, a series oscillating circuit connecting the plate and filament electrodes, a circuit connecting the grid and filament electrodes, and a resistant leak path comprising a plurality of resistance elements, means for connecting any number of said resistances between said circuits, means for inductively associating the circuits with each other, and a sound producing device included in said plate-filament circuit.

52;. An electrical tone producer including an audion having plate, grid and filament electrodes, a series oscillating circuit connecting the plate and filament electrodes, a connecting the grid and filament electrodes, and a resistance leak path comprising a plur lity of resistance elements, means for conany number of seio resistances beil circuits, mea. s for inductivel the circuits with each other, an -iesponsive device i Lied in on circuits for conve ting the ca rren us into sound n electrical tone 'r o cui i.

a J hei cl a Y. '1 .01 Mia-.11 1 tilt:

lice llitlilflti. in one o;

ti mg curcnt a1 muons waves.

an i electrodes, a circuit connecting said grid and filament electrodes, and a circuit connecting said plate and filament electrodes, means ineluded in said circuits whereby said audion and circuits become a source of continuous oscillations, and mums comprising a plurality of resistance elements selectively con nccted in one ot'said circuits for varying the current flowing therethrough, and an electro-responsive device included in one of said circuits for translating said current variations into sound Waves.

5. An electrical tone producer comprising an audion having plate, grid and filament electrodes, and circuits associated therewith having means whereby said audion and circuits become a source of sustained oscillations, and means comprising a plurality of resistances selectively inserted in one of said circuits for varying the current flowing thercthrough, and an elcctro-responsive device included in one of said circuits for translating said current variations into sound Waves, and independent means included in another of said circuits for regulating the pitch of the tones produced.

In testimony whereof I have hereunto set my hand on this 21st day of April A. D., 1915.

LEE. DE ronEs'r.

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